Android多线程下载单个文件和断点续传
实现要点：
（1）创建一个线程数组用于多个线程同时开工下载
（2）通过http连接获取文件的大小信息，然后按照线程个数来分配各个线程下载的文件片段
（3）通过http的Range头来请求文件的片段
（4）用一个map表来记录每个线程下载的信息，保存到sqlite数据库里面，用于断点续传的实现，当下载中断，可以从map表的位置开始下载
DBOpenHelper类：数据库操作
import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DBOpenHelper extends SQLiteOpenHelper { private static final String DBNAME = "eric.db"; private static final int VERSION = 1; public DBOpenHelper(Context context) { super(context, DBNAME, null, VERSION); } @Override public void onCreate(SQLiteDatabase db) { // 创建filedownlog表 db.execSQL("CREATE TABLE IF NOT EXISTS filedownlog (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, downlength INTEGER)"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS filedownlog"); onCreate(db); } }
FileService类：从数据库读写数据，封装成为map表操作
import java.util.HashMap; import java.util.Map; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import com.scofield.oneeng.db.DBOpenHelper; /** * 业务bean * */ public class FileService { private DBOpenHelper openHelper; public FileService(Context context) { openHelper = new DBOpenHelper(context); } /** * 获取每条线程已经下载的文件长度 * * @param path * @return */ public Map<Integer, Integer> getData(String path) { SQLiteDatabase db = openHelper.getReadableDatabase(); Cursor cursor = db .rawQuery( "select threadid, downlength from filedownlog where downpath=?", new String[] { path }); Map<Integer, Integer> data = new HashMap<Integer, Integer>(); while (cursor.moveToNext()) { data.put(cursor.getInt(0), cursor.getInt(1)); } cursor.close(); db.close(); return data; } /** * 保存每条线程已经下载的文件长度 * * @param path * @param map */ public void save(String path, Map<Integer, Integer> map) {// int threadid, // int position SQLiteDatabase db = openHelper.getWritableDatabase(); db.beginTransaction(); try { for (Map.Entry<Integer, Integer> entry : map.entrySet()) { db.execSQL( "insert into filedownlog(downpath, threadid, downlength) values(?,?,?)", new Object[] { path, entry.getKey(), entry.getValue() }); } db.setTransactionSuccessful(); } finally { db.endTransaction(); } db.close(); } /** * 实时更新每条线程已经下载的文件长度 * * @param path * @param map */ public void update(String path, int threadId, int pos) { SQLiteDatabase db = openHelper.getWritableDatabase(); db.execSQL( "update filedownlog set downlength=? where downpath=? and threadid=?", new Object[] { pos, path, threadId }); db.close(); } /** * 当文件下载完成后，删除对应的下载记录 * * @param path */ public void delete(String path) { SQLiteDatabase db = openHelper.getWritableDatabase(); db.execSQL("delete from filedownlog where downpath=?", new Object[] { path }); db.close(); } }
DownloadThread类：下载线程类，根据下载的位置来下载文件，并且保存到临时文件里面
import java.io.File; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import android.util.Log; public class DownloadThread extends Thread { private static final String TAG = "DownloadThread"; private File saveFile; private URL downUrl; private int block; /* 下载开始位置 */ private int threadId = -1; private int downLength; private boolean finish = false; private FileDownloader downloader; public DownloadThread(FileDownloader downloader, URL downUrl, File saveFile, int block, int downLength, int threadId) { this.downUrl = downUrl; this.saveFile = saveFile; this.block = block; this.downloader = downloader; this.threadId = threadId; this.downLength = downLength; } @Override public void run() { if (downLength < block) {// 未下载完成 try { HttpURLConnection http = (HttpURLConnection) downUrl.openConnection(); http.setConnectTimeout(5 * 1000); // 设置连接超时 http.setRequestMethod("GET"); // 设置请求方法，这里是“GET” // 浏览器可接受的MIME类型 http.setRequestProperty( "Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*"); http.setRequestProperty("Accept-Language", "zh-CN"); // 浏览器所希望的语言种类，当服务器能够提供一种以上的语言版本时要用到 http.setRequestProperty("Referer", downUrl.toString());// 包含一个URL，用户从该URL代表的页面出发访问当前请求的页面。 http.setRequestProperty("Charset", "UTF-8"); // 字符集 int startPos = block * (threadId - 1) + downLength;// 开始位置 int endPos = block * threadId - 1;// 结束位置 http.setRequestProperty("Range", "bytes=" + startPos + "-" + endPos);// 设置获取实体数据的范围 // 浏览器类型，如果Servlet返回的内容与浏览器类型有关则该值非常有用。 http.setRequestProperty( "User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)"); http.setRequestProperty("Connection", "Keep-Alive"); // 设置为持久连接 // 得到输入流 InputStream inStream = http.getInputStream(); byte[] buffer = new byte[1024]; int offset = 0; print("Thread " + this.threadId + " start download from position " + startPos); // 随机访问文件 RandomAccessFile threadfile = new RandomAccessFile( this.saveFile, "rwd"); // 定位到pos位置 threadfile.seek(startPos); while (!downloader.getExit() && (offset = inStream.read(buffer, 0, 1024)) != -1) { // 写入文件 threadfile.write(buffer, 0, offset); downLength += offset; // 累加下载的大小 downloader.update(this.threadId, downLength); // 更新指定线程下载最后的位置 downloader.append(offset); // 累加已下载大小 } threadfile.close(); inStream.close(); print("Thread " + this.threadId + " download finish"); this.finish = true; } catch (Exception e) { this.downLength = -1; print("Thread " + this.threadId + ":" + e); } } } private static void print(String msg) { Log.i(TAG, msg); } /** * 下载是否完成 * * @return */ public boolean isFinish() { return finish; } /** * 已经下载的内容大小 * * @return 如果返回值为-1,代表下载失败 */ public long getDownLength() { return downLength; } }
FileDownloader类：文件下载管理器，获取文件大小，分配和启动下载线程，监听下载的结果
import java.io.File; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; import java.util.LinkedHashMap; import java.util.Map; import java.util.UUID; import java.util.concurrent.ConcurrentHashMap; import java.util.regex.Matcher; import java.util.regex.Pattern; import android.content.Context; import android.util.Log; /** * 文件下载器 * */ public class FileDownloader { private static final String TAG = "FileDownloader"; private Context context; private FileService fileService; /* 停止下载 */ private boolean exit; /* 已下载文件长度 */ private int downloadSize = 0; /* 原始文件长度 */ private int fileSize = 0; /* 线程数 */ private DownloadThread[] threads; /* 本地保存文件 */ private File saveFile; /* 缓存各线程下载的长度 */ private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>(); /* 每条线程下载的长度 */ private int block; /* 下载路径 */ private String downloadUrl; /** * 获取线程数 */ public int getThreadSize() { return threads.length; } /** * 退出下载 */ public void exit() { this.exit = true; } public boolean getExit() { return this.exit; } /** * 获取文件大小 * * @return */ public int getFileSize() { return fileSize; } /** * 累计已下载大小 * * @param size */ protected synchronized void append(int size) { downloadSize += size; } /** * 更新指定线程最后下载的位置 * * @param threadId * 线程id * @param pos * 最后下载的位置 */ protected synchronized void update(int threadId, int pos) { this.data.put(threadId, pos); this.fileService.update(this.downloadUrl, threadId, pos); } /** * 构建文件下载器 * * @param downloadUrl * 下载路径 * @param fileSaveDir * 文件保存目录 * @param threadNum * 下载线程数 */ public FileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) { try { this.context = context; this.downloadUrl = downloadUrl; fileService = new FileService(this.context); URL url = new URL(this.downloadUrl); if (!fileSaveDir.exists()) // 判断目录是否存在，如果不存在，创建目录 fileSaveDir.mkdirs(); this.threads = new DownloadThread[threadNum];// 实例化线程数组 HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); conn.setRequestProperty( "Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*"); conn.setRequestProperty("Accept-Language", "zh-CN"); conn.setRequestProperty("Referer", downloadUrl); conn.setRequestProperty("Charset", "UTF-8"); conn.setRequestProperty( "User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)"); conn.setRequestProperty("Connection", "Keep-Alive"); conn.connect(); // 连接 printResponseHeader(conn); if (conn.getResponseCode() == 200) { // 响应成功 this.fileSize = conn.getContentLength();// 根据响应获取文件大小 if (this.fileSize <= 0) throw new RuntimeException("Unkown file size "); String filename = getFileName(conn);// 获取文件名称 this.saveFile = new File(fileSaveDir, filename);// 构建保存文件 Map<Integer, Integer> logdata = fileService .getData(downloadUrl);// 获取下载记录 if (logdata.size() > 0) {// 如果存在下载记录 for (Map.Entry<Integer, Integer> entry : logdata.entrySet()) data.put(entry.getKey(), entry.getValue());// 把各条线程已经下载的数据长度放入data中 } if (this.data.size() == this.threads.length) {// 下面计算所有线程已经下载的数据总长度 for (int i = 0; i < this.threads.length; i++) { this.downloadSize += this.data.get(i + 1); } print("已经下载的长度" + this.downloadSize); } // 计算每条线程下载的数据长度 this.block = (this.fileSize % this.threads.length) == 0 ? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1; } else { throw new RuntimeException("server no response "); } } catch (Exception e) { print(e.toString()); throw new RuntimeException("don't connection this url"); } } /** * 获取文件名 */ private String getFileName(HttpURLConnection conn) { String filename = this.downloadUrl.substring(this.downloadUrl .lastIndexOf('/') + 1); if (filename == null || "".equals(filename.trim())) {// 如果获取不到文件名称 for (int i = 0;; i++) { String mine = conn.getHeaderField(i); if (mine == null) break; if ("content-disposition".equals(conn.getHeaderFieldKey(i) .toLowerCase())) { Matcher m = Pattern.compile(".*filename=(.*)").matcher( mine.toLowerCase()); if (m.find()) return m.group(1); } } filename = UUID.randomUUID() + ".tmp";// 默认取一个文件名 } return filename; } /** * 开始下载文件 * * @param listener * 监听下载数量的变化,如果不需要了解实时下载的数量,可以设置为null * @return 已下载文件大小 * @throws Exception */ public int download(DownloadProgressListener listener) throws Exception { try { RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw"); if (this.fileSize > 0) randOut.setLength(this.fileSize); // 预分配fileSize大小 randOut.close(); URL url = new URL(this.downloadUrl); if (this.data.size() != this.threads.length) {// 如果原先未曾下载或者原先的下载线程数与现在的线程数不一致 this.data.clear(); for (int i = 0; i < this.threads.length; i++) { this.data.put(i + 1, 0);// 初始化每条线程已经下载的数据长度为0 } this.downloadSize = 0; } for (int i = 0; i < this.threads.length; i++) {// 开启线程进行下载 int downLength = this.data.get(i + 1); if (downLength < this.block && this.downloadSize < this.fileSize) {// 判断线程是否已经完成下载,否则继续下载 this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i + 1), i + 1); this.threads[i].setPriority(7); // 设置线程优先级 this.threads[i].start(); } else { this.threads[i] = null; } } fileService.delete(this.downloadUrl);// 如果存在下载记录，删除它们，然后重新添加 fileService.save(this.downloadUrl, this.data); boolean notFinish = true;// 下载未完成 while (notFinish) {// 循环判断所有线程是否完成下载 Thread.sleep(900); notFinish = false;// 假定全部线程下载完成 for (int i = 0; i < this.threads.length; i++) { if (this.threads[i] != null && !this.threads[i].isFinish()) {// 如果发现线程未完成下载 notFinish = true;// 设置标志为下载没有完成 if (this.threads[i].getDownLength() == -1) {// 如果下载失败,再重新下载 this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i + 1), i + 1); this.threads[i].setPriority(7); this.threads[i].start(); } } } if (listener != null) listener.onDownloadSize(this.downloadSize);// 通知目前已经下载完成的数据长度 } if (downloadSize == this.fileSize) fileService.delete(this.downloadUrl);// 下载完成删除记录 } catch (Exception e) { print(e.toString()); throw new Exception("file download error"); } return this.downloadSize; } /** * 获取Http响应头字段 * * @param http * @return */ public static Map<String, String> getHttpResponseHeader( HttpURLConnection http) { Map<String, String> header = new LinkedHashMap<String, String>(); for (int i = 0;; i++) { String mine = http.getHeaderField(i); if (mine == null) break; header.put(http.getHeaderFieldKey(i), mine); } return header; } /** * 打印Http头字段 * * @param http */ public static void printResponseHeader(HttpURLConnection http) { Map<String, String> header = getHttpResponseHeader(http); for (Map.Entry<String, String> entry : header.entrySet()) { String key = entry.getKey() != null ? entry.getKey() + ":" : ""; print(key + entry.getValue()); } } private static void print(String msg) { Log.i(TAG, msg); } }